<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div id="app">

    <div v-if="count == 1">div1</div>
    <div v-if="count == 2">div2</div>
    <div v-if="count == 3">div3</div>

    <br>
    <div v-show="count==30">div-show</div>
    <br>
    <input v-model="count">

</div>
<script src="js/vue.js"></script>
<script>
    //1.创建vue对象
    new Vue({
        el: "#app",
        data() { //简化书写
            return {
                username: "",
                url: "https://www.baidu.com",
                count:3
            }
        }
    });
</script>
</body>
</html>